The problem with the Tang is that they don't really have the same "Rise" that Rome did. They just kinda took over from the Sui, who had already had most of Han Chinese lands under their control (an area the size of western Europe). The also didn't have the same cataclysmic "Fall" that western Rome did, with mass migrations, invasions, and wars with rival powers. They just fractured from internal instability.
The Tang fought a bunch of people, but these were all wars on the periphery, not ever something that required the empire to go on a war footing. These were all military expeditions a la The Last Roman.
The one big exception would be the An Lushang rebellion. I could definitely see that as being a great campaign. It involved basically every nation in the region, and was the closest the Tang dynasty came to destruction before the actual end of the dynasty.
As for the Three Kingdoms, its fine as a full game. We already have the Shogun games to show that you don't have to have a long time period or massive map scale to make a tentpole Total War. The problem with trying to make the whole Han Dynasty into a game is that nobody else in the region was even close to it in power. Any game as the Han when they were united would be a massive unbalanced campaign, without the Attila era's excuse to debuff the Romans. The Three Kingdoms works because the scope is still epic but the fracturing of power means that factions can start on a more even footing, and basically everywhere is fighting, not just the periphery of the empire.